1. Field of the Invention
This invention relates to optical systems having optical path bending means and, more particularly, to cameras such as photographic cameras or video cameras employing the same. Still more particularly, it relates to a reflex camera suited to achieve a minimization of the size of the entirety of the camera by reducing its vertical thickness.
2. Description of the Related Art
The conventional single-lens reflex type of photographic camera or video camera has its optical system formed as shown in FIG. 1, where a photosensitive plane 53 is arranged on the optical axis of a photographic lens 51 and located behind it to constitute the photographic system.
The optical system further includes a turnable mirror 52, when positioned in between the photographic lens 51 and the photosensitive plane 53, to reflect the light beam entering through the photographic lens 51 to the upper portion of the camera body so that a finder image is formed on a focusing screen 54. Then, the finder image on the focusing screen 54 is observed through a condenser lens 55 and a pentagonal roof type prism 56 so that an erecting non-reverse image appears in an eyepiece lens 57. The finder system is thus constructed and arranged.
It is appreciated that in the conventional single-lens reflex camera, the finder image-bearing beam is reflected upward to the upper portion of the camera body by the turnable mirror 52, and the pentagonal roof type prism 56 arranged as protruding upward from the photographic lens 51 is used to obtain the finder image in the erecting non-reverse attitude. For this reason, the pentagonal roof type prism 56, though constituting only part of the finder system, must be housed as an awkward projection on the upper portion of the camera body. When the photographic lens 51 is attached to the camera body, therefore, the entirety of the camera tends to become relatively big in size.
Meanwhile, Japanese Laid-Open Patent Application No. Sho 54-99623 or Japanese Utility Model Publication No. Sho 54-8736 discloses an optical system which allows the height of the above-described conventional common type of single-lens reflex camera to be shortened. To attain the erecting non-reverse image (correct image) in the viewfinder, however, the total longitudinal length of the camera body is elongated.
In Japanese Laid-Open Patent Application Sho 60-114841, too, there is also disclosed a single-lens reflex camera of shortened height. However, the use of the disclosed technique for meeting the requirement of obtaining the correct image in the viewfinder causes, conversely, the lateral length to increase.